Applications of Array Pointers (1A) Young Won Lim 11/22/18

Transcription

1 Appliations of Array Pointers (1A)

2 Copyright () Young W. Lim. Permission is granted to opy, distribute and/or modify this doument under the terms of the GNU Free Doumentation Liense, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Setions, no Front-Cover Texts, and no Bak-Cover Texts. A opy of the liense is inluded in the setion entitled "GNU Free Doumentation Liense". Please send orretions (or suggestions) to youngwlim@hotmail.om. This doument was produed by using LibreOffie.

3 Pointer to Multi-dimensional Arrays of Array Pointers 3

4 Integer pointer type (int (*)[4]) type an point only to int [4] type an int array name a pointer to a pointer (int **) *) (int *) a pointer to an int (int [4]) *) an int array name a pointer to a 1-d array (int (*)[4]) 1-d array pointer int [4] = (int [ ] int *) eah of these types points to an int type data of Array Pointers 4

5 Series of array pointers a type view a pointer to a 1-d array a pointer to a 1-d array a pointer to a 1-d array (int (*)[4]) (int (*)[4]) (int (*)[4]) 1-d array pointers (int [4]) *) the name of a 1-d int array (int [4]) *) the name of a 1-d int array (int [4]) *) the name of a 1-d int array of Array Pointers 5

6 Series of array pointers 1-d arrays a, b, int a[4]; int (*r); int b[4]; int [4]; (int *) r taking no memory loations a b a a a a b b b b assume that array a, b, and are ontiguous of Array Pointers 6

7 Series of array pointers array pointers p1, p2, p3 int (*p1)[4]; int (*p2)[4]; int (*p3)[4]; assignment p1 = &a p2 = &b p3 = & a pointer to a 1-d array a pointer to a 1-d array a pointer to a 1-d array 1-d array pointers p1 p2 p3 1-d arrays taking no memory loations a b a a a a b b b b assume that array p1, p2, and p3 are ontiguous assume that array a, b, and are ontiguous of Array Pointers 7

8 Series of array pointers 1-d arrays via p1, p2, p3 a pointer to a 1-d array a pointer to a 1-d array a pointer to a 1-d array equivalene (*p1) p1 a (*p2) p2 b (*p3) p3 p1 p2 p3 1-d array pointers taking no memory loations p1 p2 p3 p1 p1 p1 p1 p2 p2 p2 p2 assume that array a, b, and are ontiguous of Array Pointers 8

9 Series of array pointers a variable view int a[4]; int (*p1)[4]; int (*r); int b[4]; int (*p2)[4]; int [4]; int (*p3)[4]; assignment p1 = &a p2 = &b p3 = & a pointer to a 1-d array a pointer to a 1-d array a pointer to a 1-d array equivalene (*p1) p1 a (*p2) p2 b (*p3) p3 p1 p2 p3 1-d array pointers (int *) r taking no memory loations a b a a a a b b b b assume that array a, b, and are ontiguous in the memory of Array Pointers 9

10 Extending a 1-d pointer array a variable view int (*q)[4][4]; (int (*)[4]) q (int *) [4]) q an array of 1-d arrays q+1 (int *) [4]) q q+2 (int *) [4]) q assignment q = a q = b q = equivalene q *(q+0) a q *(q+1) b q *(q+2) taking onseutive memory loations 1-d array names assume arrays a, b, are onseutive q q q q q q q q q q q q of Array Pointers 10

11 1-d array pointer to onseutive 1-d arrays int (*p)[4]; a pointer to a pointer array p 1-d array pointer assignment p = &a equivalene *(p+0) p a *(p+1) p b *(p+2) p *(p+2) p d if arrays a, b,, d are onseutive p+0 p+1 p+2 p+3 p p p p p p p p p p p p p p p p p p p p of Array Pointers 11

12 A 2-d array and its sub-arrays array name int [4][4]; : the 2-d array name the 2-d array starting address the 1-d array pointer points to its 1 st 1-d sub-array ompilers do not alloate s memory loation a 2-d array with 4 rows and 4 olumns of Array Pointers 12

13 A 2-d array and its sub-arrays subarray names int [4][4]; [i] the 1-d array name the 1-d array starting address the 0-d array pointer points to its salar integer the 1 st 1-d subarray name the 2 nd 1-d subarray name the 3 rd 1-d subarray name the 4 th 1-d subarray name ompilers do not alloate [i] s memory loation a 2-d array with 4 rows and 4 olumns of Array Pointers 13

14 A 2-d array and its sub-arrays type sizes sizeof() = 4*4*4 bytes sizeof([i]) = 4*4 bytes sizeof([i][j]) = 4 bytes [i] [i][j] : the 2-d array name : the 1-d array name : the 0-d array name (a salar integer) a 2-d array with 4 rows and 4 olumns of Array Pointers 14

15 A 2-d array and its 1-d sub-arrays a type view 2-d array name int (*) [4] 1-d array pointer int (*) [4] 1-d subarray name int [4] 1-d subarray name int [4] 1-d subarray name int [4] 1-d subarray name int [4] and different types the same address of the starting element a 2-d array with 4 rows and 4 olumns (int (*) [4]) (int [4]) (int [4]) (int [4]) (int [4]) of Array Pointers 15

16 1-d subarray aggregated data type The 1 st subarray (=subarray name) sizeof() = 4*4 bytes (+0) : start address The 2 nd subarray (=subarray name) sizeof() = 4*4 bytes (+1) : start address The 3 rd subarray (=subarray name) sizeof() = 4*4 bytes (+2) : start address The 4 th subarray (=subarray name) sizeof() = 4*4 bytes (+3) : start address (int []) (int []) (int []) (int []) of Array Pointers 16

17 2-d array name as a pointer to a 1-d subarray 2-d array name 1-d array pointer 1-d array pointer +1 1-d array pointer +2 1-d array pointer +3 (int (*) [4]) (int (*) [4]) (int (*) [4]) (int (*) [4]) (int []) (int []) (int []) The 1 st subarray The 2 nd subarray The 3 rd subarray +3 (int []) The 4 th subarray of Array Pointers 17

18 1-d array and 0-d and 1-d array pointers 0-d array pointer : int pointer 1-d array pointer 0-d 1-d int (*m) ; int (*n) [4] ; int [4] ; int [4] ; (int (*)) m = ; (int(*)[4]) n = &; m = &; m[i] [i] (*n)[i] n[i] [i] of Array Pointers 18

19 2-d array and 1-d and 2-d array pointers 1-d array pointer 2-d array pointer 1-d 2-d int (*p) [4] ; int (*q) [4][4] ; int [4] [4] ; int [4][4] ; (int (*) [4]) p = ; p = &; (int(*)[4][4]) q = &; p[i] [i] (*q)[i][j] q[i][j] [i][j] of Array Pointers 19

20 1-d array pointer to the 1-d subarray of a 2-d array 1-d array pointer &p (int (*) [4]) p int (*p)[4] = ; p = ; An array pointer: sizeof(p) = 8 bytes 1-d sub-arrays : sizeof(*p) = 4*4 bytes q+1 (int (*) [4]) (int []) (int []) (int []) (int []) of Array Pointers 20

21 2-d array pointer to a 2-d array 2-d array pointer &q (int(*)[4][4]) q int (*q)[4][4] = &; q = &; An array pointer: sizeof(q) = 8 bytes 1-d sub-arrays : sizeof(*q) = 4*4*4 bytes q+1 (int (*) [4]) (int []) (int []) (int []) (int []) of Array Pointers 21

22 Using a 1-d array pointer to a 2-d array int (*p) [4] ; int [4] [4] 1-d array pointer &p (int (*) [4]) p p = ; p[i] [i] 1-d a 2-d array with 4 rows and 4 olumns (int (*) [4]) p p p p p p p p p p p p p p p p p p p p p p p p p of Array Pointers 22

23 Using a 2-d array pointer to a 2-d array int (*q) [4][4] ; int [4][4] ; 2-d array pointer &p (int(*)[4][4]) q q = &; (*q)[i] [i] 2-d a 2-d array with 4 rows and 4 olumns *q (int (*) [4]) C *q (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) (*q) of Array Pointers 23

24 (n-1)-d array pointer to a n-d array int a[4] ; 1-d array int (*p) ; 0-d array pointer (p = a) int b[4] ; 2-d array int (*q) ; 1-d array pointer (q = b) int [4] ; 3-d array int (*r) ; 2-d array pointer (r = ) int d[4] [4]; 4-d array int (*s) [4]; 3-d array pointer (s = d) of Array Pointers 24

25 n-d array name and (n-1)-d array pointer int a[4] ; p = &a; int (*p) ; p = a; p a a a int b[4] ; q = &b; int (*q) ; q = b; q b b b int [4] ; r = &; int (*r) ; r = ; r int d[4] [4]; s = &d; int (*s) [4]; s = d; s d d d of Array Pointers 25

26 n-d array pointer to a n-d array int a [4] ; 1-d array int (*p) [4]; 1-d array pointer (p = &a) int b [4]; 2-d array int (*q) [4]; 2-d array pointer (q = &b) int [4]; 3-d array int (*r) [4]; 3-d array pointer (r = &) int d [4][4]; 4-d array int (*s) [4][4]; 4-d array pointer (s = &d) of Array Pointers 26

27 n-d array name and n-d array pointer int a [4] ; p = &a; int (*p) [4]; &a p a a int b [4]; q = &b; int (*q) [4]; &b q b b int [4]; r = &; int (*r) [4]; & r int d [4][4]; s = &d; int (*s) [4][4]; &d s d d of Array Pointers 27

28 multi-dimensional array pointers p a q b r a a b a b b int a[4] ; 1-d array int (*p) ; 0-d array pointer int b[4] ; 2-d array int (*q) ; 1-d array pointer int [4] ; 3-d array int (*r) ; 2-d array pointer a b int d[4] [4]; 4-d array int (*s) [4]; 3-d array pointer of Array Pointers 28

29 Initializing multi-dimensional array pointers (1) p1 q2 r3 &a &b & a int a[4] ; int (*p1)[4] = &a ; b b int b[4]; int (*q2)[4] = &b; a int [4]; int (*r3)[4] = &; s4 &d d int d[4][4]; int (*s4)[4][4] = &d; d of Array Pointers 29

30 Initializing multi-dimensional array pointers (2) p0 q1 r2 a int a[4] ; int (*p0) = a ; b b int b[4]; int (*q1) = b; a int [4]; int (*r2) = ; s3 int d[4][4]; int (*s3)[4] = d; d d of Array Pointers 30

31 multi-dimensional array pointers int d[4] [4]; int (*s) [4]; d 4-d array name d[4][4] 3-d array pointer (*p)[4] d[i] 3-d array name d[i][4] 2-d array pointer (*q)[4] d[i][j] 2-d array name d[i][j][4] 1-d array pointer (*r)[4] d[i][j][k] 1-d array name d[i][j][k][4] 0-d array pointer (*s) i =[0..3], j = [0..1], k= [0..2] s d of Array Pointers 31

32 multi-dimensional array pointers int d[4] [4]; int (*s) [4]; d 4-d array name d[4][4] p[i][j][k][l] 3-d array pointer (*p)[4] int (*p)[4] = d; d[i] 3-d array name d[i][4] q[j][k][l] 2-d array pointer (*q)[4] int (*q)[4] = d[i]; d[i][j] 2-d array name d[i][j][4] r[k][l] 1-d array pointer (*r)[4] int (*r)[4] = d[i][j]; d[i][j][k] 1-d array name d[i][j][k][4] s[l] 0-d array pointer (*s) int (*s) = d[i][j][k]; i =[0..3], j = [0..1], k= [0..2] of Array Pointers 32

33 Passing multidimensional array names int a[4] ; int (*p) ; all funa(a, ); prototype void funa(int (*p), ); int b[4] ; int (*q) ; all funb(b, ); prototype void funb(int (*q), ); int [4] ; int (*r) ; all fun(, ); prototype void fun(int (*r), ); int d[4] [4]; int (*s) [4]; all fund(d, ); prototype void fund(int (*s)[4], ); of Array Pointers 33

34 Referenes Essential C, Nik Parlante Effiient C Programming, Mark A. Weiss C A Referene Manual, Samuel P. Harbison & Guy L. Steele Jr. [4] C Language Express, I. K. Chun